Sounds like I lost the com processor reading some of the other posts on this topic.the upload fails but the loop back test passed ok, no tx or rx leds, Uno runs my last skecth ok and blinks the led on resetAny hope of salvaging this UNO r3 or is it ready for the trash can?

Here is something that may be related to this. Go into the "Control Panel > Hardware >System > Device manager", and click on "View > Show hidden devices".

What you will probably see is a list of COM ports which aren't even connected to thecomputer, but had been connected some time in the past. [B.Gates never seems to forget, and rarely does any garbage-connection either, it would seem - similar for theinfamous Temp folder under Local Settings].

On my 7-YO notebook, the first time I did this, there were maybe 50 items shown there. The best I can figure is, every time you plug a device into a "different" USB port than the previous time, Windose assigns a new COM# to it, and adds one more item to the list, and which is never removed.

I now have labels on my USB hub ports so I always plug the same device into the same port.